Human infants grow up in environments populated by artifacts. In order to acquire knowledge about different kinds of human-made objects, children have to be able to focus on the information that is most relevant for sorting artifacts into categories. Traditional theories emphasize the role of superficial, perceptual features in object categorization. In the case of artifacts, however, it is possible that abstract, non-obvious properties, like functions, may form the basis of artifact kind representations from an early age. Using an object individuation paradigm we addressed the question whether non-verbal communicative demonstration of the functional use of artifacts makes young infants represent such objects in terms of their kinds. When two different functions were sequentially demonstrated on two novel objects as they emerged one-by-one from behind a screen, 10-month-old infants inferred the presence of two objects behind the occluder. We further show that both the presence of communicative signals and causal intervention are necessary for 10-month-olds to generate such a numerical expectation. We also found that communicative demonstration of two different functions of a single artifact generated the illusion of the presence of two objects. This suggests that information on artifact function was used as an indicator of kind membership, and infants expected one specific function to define one specific artifact kind. Thus, contrary to previous accounts, preverbal infants' specific sensitivity to object function underlies, guides, and supports their learning about artifacts.